1. Technical Field of the Invention
This invention relates to a single roll crusher for comminution of high purity materials, such as polycrystalline silicon.
2. Background
Most semiconductor chips used in electronic devices are fabricated from single crystal silicon prepared by a Czochralski-type (CZ) process. In the CZ process, a single crystal silicon ingot is produced by melting polycrystalline silicon source material in a crucible, stabilizing the crucible and source melt at an equilibrium temperature, dipping a seed crystal into the source melt, withdrawing the seed crystal as the source melt crystallizes on the seed to form a single crystal ingot, and pulling the ingot as it grows. Melting occurs at a temperature of 1420° C. in an inert gas environment at low pressure. The crucible is continually rotated about a generally vertical axis as the crystal grows. The rate at which the ingot is pulled from the source melt is selected to form an ingot having a desired diameter.
Polycrystalline silicon rods useful as or for preparing the source material can be prepared by methods known in the art. For example, polycrystalline silicon rods can be prepared by a chemical vapor deposition (CVD) process comprising chemical vapor deposition of a high purity chlorosilane or silane gas onto a heated substrate, see Handbook of Semiconductor Silicon Technology, edited by William C. O'Mara, Robert B. Herring, and Lee P. Hunt, Noyes Publications, Park Ridge, N.J., U.S.A., 1990, Ch. 2, pp. 39-58. The polycrystalline silicon prepared by the CVD process can be comminuted into suitably sized pieces such as rods, chunks, chips, and combinations thereof, before loading into the crucible. The polycrystalline silicon is melted to form the molten silicon.
Methods to comminute the polycrystalline silicon rods to prepare the chunks, chips, and other suitably sized pieces suffer from various drawbacks. The polycrystalline silicon rods can be comminuted, for example, by striking with a low-contamination impact tool such as that disclosed in EP 0 539 097 A1. This is a labor intensive process. Alternatively, the polycrystalline silicon rods may be comminuted using a jaw crusher. Jaw crushers may be inefficient when used to comminute polycrystalline silicon, for example, up to 3% of the polycrystalline silicon may be lost as dust and fines too small to be useful in the CZ process. Alternatively, the polycrystalline silicon rods may be comminuted by striking with a low-contamination impact tool and the resulting comminuted rods may be further comminuted using a jaw crusher.